A vehicle airbag assembly commonly includes an inflator, an airbag, a cover, and a reaction device which cooperate to protect a vehicle occupant in the event of a crash or collision. The airbag assembly is generally mounted to a structural part of a vehicle via the reaction device. In the case of a passenger side airbag assembly, for example, the reaction device may be mounted to the support structure for the vehicle instrument panel. The cover, which separates the remaining components of the airbag assembly from an occupant compartment, is usually designed to form a part of the vehicle instrument panel.
When mounted to a vehicle, an airbag assembly operates to deploy an airbag at the onset of a vehicle collision. Specifically, at the onset of a collision, an inflator supplies inflation fluid to the airbag. This supply of inflation fluid expands the airbag to sequentially (although almost instantaneously) create an opening in the cover, force the airbag through the opening into the occupant compartment, and fully inflate the airbag to cushion an occupant against impact with a structural part of the vehicle. A heat shield may be incorporated into the airbag assembly to protect the vehicle from heat transferred by the inflator during deployment.
In the airbag industry, the development of new and more cost-effective methods for making airbag assemblies is becoming increasingly important. More particularly, airbag assemblies are currently being installed in a large number of automobiles. As consumer demand and federal regulatory requirements for vehicle safety continue to escalate, the number of airbag assemblies installed in the future will continue to increase. To enable auto-makers to meet this growing demand, there is a continuing need for simple and effective techniques which lend themselves to the efficient and economical production of airbag assemblies.
One factor which affects the cost and complication of production is the fabrication of the individual components of an airbag assembly. In many existing airbag assemblies, certain components, such as the reaction device and/or the heat shield, are multi-piece structures formed by bolting, riveting or welding several pieces together. While such multi-piece structures have proven satisfactory, the associated fabrication techniques are sometimes quite complicated and time-consuming. More specifically, in the fabrication of a multi-piece structure, it is necessary to align or position the various components in correct orientations and then bolt, rivet, or weld these aligned components to each other.
Additionally, irrespective of whether a component is a multi-piece structure, coupling holes must usually be formed in the component to receive primary fastening elements of the airbag assembly. The location of these coupling holes (and other features which must be formed by further processing) are often such that they must be formed by multi-directional piercing or punching. Consequently, it is often necessary to align or position the component in a plurality of orientations to perform these further processing steps.
Another factor which affects the cost and complication of production is the incorporation of the inflator into the airbag assembly. The inflator is generally the heaviest component of the airbag assembly and thus an early incorporation of this component is usually undesirable. Moreover, the transportation and/or storage of inflators often involves compliance with certain safety regulations which are inapplicable to the other components of the airbag assembly. Accordingly, many manufacturers prefer to incorporate the inflator into the airbag assembly at a later stage and/or a different location than the other components of the airbag assembly.
Yet another factor which influences production efficiency is the assembly of the individual components of an airbag assembly together. In a typical assembly process, the airbag is coupled to the reaction device with a set of fastening elements (such as bolts or rivets), and the cover is coupled to the reaction device with an additional set of fastening elements. If the airbag assembly includes a heat shield, this component is also coupled to the reaction device with fastening elements.
Generally, the more separate fastening elements incorporated into an airbag assembly, the more complicated the assembly technique. Although some airbag assembly designs have used one set of fastening elements to couple both the airbag and the cover together, such designs require twenty or more separate fastening elements per airbag assembly. (See e.g., U.S. Pat. No. 5,121,941. Additionally, in many airbag assemblies, the only option for fastening elements is blind rivets which prevent visual inspection of the locking portions of the fastening elements.
For these reasons, applicants believe a need remains for an airbag assembly which (i) avoids the complicated fabrication techniques associated with multi-piece structures and/or multi-directional piercing; (ii) allows the incorporation of the inflator into the airbag assembly at a later time and/or a different location than the other components of the airbag assembly; and (iii) minimizes the number of fastening elements and eliminates the need for blind rivets.